External users in Teams Shared Channel get Entra ID error when opening video files (Access to application denied)

This behavior is consistent with how externally shared video access works in Microsoft 365.

If the video is stored in a location that can’t be shared with external users, external participants can get access failures even though other files in the shared channel work. For SharePoint/Stream video scenarios, the supported workaround is to store the video in a SharePoint Online or OneDrive location that enables external sharing, and then share the video from that location.

For a Teams shared channel scenario, use this path:

1. Verify where the video file is actually stored.
   • If it remains in another SharePoint site or location that external users can’t access, opening it from the shared channel can still redirect access to that original location.
2. Move or upload the video into the SharePoint site that backs the shared channel, or another SharePoint Online/OneDrive location that allows external sharing.
   • The file must be stored in the externally shareable location, not just linked from there.
3. Share the video directly from that location with the external users.
   • In the accepted Microsoft Q&A guidance for this exact pattern, the recommended link setting is People you choose with Can view.
4. If the shared channel itself shows cross-tenant sharing errors, check Microsoft Entra cross-tenant access settings.
   • In Microsoft Entra ID → External Identities → Cross-tenant access settings
   • Open the inbound access settings for the external organization.
   • On B2B direct connect → Customize settings → External users and groups, confirm Allow access is enabled for the required users or groups.
5. If the error persists after the video is moved, confirm with the external organization that their outbound cross-tenant settings allow sharing with the host organization.

Key point: access to Office files in a shared channel does not guarantee native video playback will work if the video is still tied to a storage location or application path that external users can’t access. Storing the video in the shared channel’s SharePoint location and sharing it from there is the recommended workaround supported by the provided guidance.

References:

• "This video isn't available" when external user views shared video | Microsoft Support
• Shared channels errors in Microsoft Teams
• Sharing Stream (on SharePoint) video link in Teams still redirects to original SharePoint site and prompts external users for access - Microsoft Q&A